The present invention relates to a semiconductor device having a touch panel controller for controlling a touch panel, and an electronic device having a touch panel controller and a microprocessor.
An electrostatic capacitance type touch panel has been in widespread use as an input device of PDA (Personal Digital Assistant), a tablet PC (Personal computer) or the like. Especially, a mutual capacitance-type touch panel which enables a multi-touch detection includes: a plurality of drive electrodes; a plurality of detection electrodes; and a plurality of crossing parts formed by the drive electrodes and the detection electrodes, wherein a fluctuation in capacitive coupling state at each crossing part can be obtained by means of signals taken, in turn, from the detection electrodes when the drive electrodes are driven by use of a pulse in turn. Calculating the coordinates of a position where the capacitance fluctuation is caused, which crossing part the stray capacitance has been changed on, i.e. which crossing part a finger has approached or touched can be known.
International Patent Publication No. JP-T-2009-535742 includes the description for the reduction of noise in the detection cycle of an electrostatic capacitance type touch panel. Specifically, it is preferable for the purpose of noise rejection to drive a touch panel by means of drive pulses having different frequencies. Noise which is present in a drive pulse of a certain drive frequency is not involved in a drive pulse of another frequency. For instance, it suffices to perform the detecting action with drive pulses of three drive frequencies, and then to adopt, from results thereof, one which is the smallest in the influence of noise.